油气藏上方磁及自电异常成因模型

本文把油气藏上方划分为五个地球化学带。通过对地壳中含量较高的变价元素铁的分析，认为在过渡带Ⅲ＿１中将富集成岩磁铁矿，在还原柱与围岩的接触面上存在过剩电位差，可将其等效为双电层．成岩磁铁矿产生弱磁异常，双电层引起自然电位异常。从而把磁法和自然电场法直接找油气的理论统一为变价元素铁在不同的环境下所发生的物理化学作用上。利用简单的几何形体代表各地球化学带建立了磁模型，把双电层等效成电偶层建立了自电模型，最后对玉门某构造上磁异常和自电异常进行了解释．

GENESIS MODEL OF MAGNETIC AND SP ANOMALIES OVER OIL AND GAS DEPOSITS

The layer over oil-gas deposits is divided into five geochemical zones in this paper. By analysing the geochemistry of multivalent element iron that is rich in the crustal rocks. we consider that more diagenetic magnetite can be formed in the transitional zone and extra potential difference is formed between reduction column and surrounding rocks. which can be equivalent to two-electric-layer. Diagenetic magnetite causes magnetic anomaly and two-electric-layer causes SP anomaly. Thus, the theory of magnetic and SP methods for searching oil-gas deposit can be unified directly as physical and chemical reaction of the multivalent element iron in different surrounding environment. We construct magnetic model using simple geometry bodies which represent various geochemical zones and SP model by simplifying two-electric-layer as electric double layer. At last, we interpret magnetic and SP anomalies over some structures in Yumen Oil Field.